1. Field of the Invention
The present invention relates to an image sensing device, more particularly, to an image sensing device which is capable of switching an auto-focus control and a manual control.
2. Description of the Related Art
In image sensing devices such as surveillance cameras, video cameras, or the like, the auto-focus control and the manual control are extensively utilized. Further, the manual control includes two types which are a manual-focus control and a manual-focus-trace control. Incidentally, in this specification, the auto-focus control is denoted by a first mode, and the manual control is denoted by a second mode.
The auto-focus control is a control for performing focus adjustment automatically by driving a focus-lens automatically. To the contrary, the manual-focus control is a control for a user to drive a focus-lens manually for performing focus adjustment. The manual-focus-trace control is a control for a user to drive the zoom-lens manually and then to drive the focus-lens automatically so as to maintain the in-focus state for the identical target object, even after the zoom-lens is traveled.
In the case of the manual-focus-trace control, when the zoom-lens is traveled, the focus-lens needs to be traveled to an exact corresponding position in order to perform focus adjustment on a target object which is located in the identical target object distance. Here, a lens in-focus trajectory data, which indicates a position of the zoom-lens and a position of the focus-lens, is utilized.
Here, the lens in-focus trajectory data is explained with reference to FIG. 4.
FIG. 4 is a diagram showing a graph of the lens in-focus trajectory data.
As shown in FIG. 4, a horizontal axis on the graph represents the position of the zoom-lens, and a vertical axis shows the position of the focus-lens. The diagram shows in-focus positions of both lenses for the identical target object distance. A plurality of curves, in accordance with the target object distance, are shown in the diagram on the tele-side position of the zoom-lens. Based on this diagram, the position of the focus-lens is determined in accordance with the position of the zoom-lens determined by the user.
On the other hand, in the case of surveillance cameras which perform a long-time video-shooting, in consideration of a life of driving the focus-lens, the manual control is mainly utilized, and is changed to the auto-focus control only if an in-focus position adjustment is required with a high precision. One example is a control method to switch from the manual control to the auto-focus control when the user issues a command or manipulates a button, thereafter, to switch back to the manual control after the in-focus position adjustment is completed. Furthermore, the other example is a control method to perform the manual control while the zoom-lens is being traveled, then subsequently to switch from the manual control to the auto-focus control immediately after the zoom-lens is traveled, thereafter to switch back to the manual control after the in-focus position adjustment is completed.
(For example, see JP 2005-62665 A, JP 2006-215285 A and JP H11-281869 A.)
JP 2005-62665 A discloses a technique to switch from the auto-focus control to the manual control immediately after the in-focus position adjustment is completed in the auto-focus control.
JP 2006-215285 A discloses a control technique to determine whether the zoom-lens is being traveled or not, to prohibit the auto-focus control while the zoom-lens is being traveled, and to enable the auto-focus control while the zoom-lens is not being traveled. Moreover, JP 2006-215285 A also describes that, in the case of performing focus adjustment on the required target object by traveling the zoom-lens to the tele-side before starting the shooting, the in-focus position can be adjusted, by disabling the auto-focus control in the wide-side, even if the zoom-lens is traveled to the tele-side.
JP H11-281869 A discloses a technique to travel the focus-lens onto an infinity tracking curve (a curve to indicate the zoom-lens position and the focus-lens position) and to fix the focus-lens when a zoom-lens operation command is issued, subsequently, to travel the zoom-lens and the focus-lens along the infinity tracking curve, then, to perform focus adjustment by the auto-focus control once the zooming operation is completed, and thereafter, to turn off the focus motor.